• Ad Astra
  • Posts
  • What happens if you look straight at an eclipse?

What happens if you look straight at an eclipse?

Here's how the sun can damage your eyes

What actually happens to your eyes if you look directly at the sun during an eclipse?

As the total eclipse on April 8, 2024 gets closer, you’re probably hearing people say again and again “get your eclipse glasses, don’t look at the sun without proper eye protection.” The way I know that is I’m one of those people.

Credit: NASA/Aubrey Gemignani

But what would actually happen to your eyes if you tried to watch the eclipse without eye protection?? And why does everyone talk about this specifically during a solar eclipse?? Let’s dive in.

How does the eye work?

Light enters the eye through your pupil, and the dilation of your pupils (thanks to your iris) controls how much light gets into your eye. The light then passes through the lens, which focuses light on a small part of the retina called the macula. That’s the key here, the macula is where your photoreceptors turn the light into electrical signals. The electrical signals travel to your brain via the optic nerve, so that’s how they’re turned into what we see.

Credit: NIH/National Eye Institute

Ok, so then what would staring at the sun do to your eyes? 

Basically the photoreceptors in your eyes will be overloaded. You might have heard people say “you’ll burn your retinas,” and that’s mostly accurate. Basically you’ll scorch the photoreceptor cells, which are key to being able to focus your eyes centrally and color vision. This means you’ll cause photochemical reactions that will damage your photoreceptors, thanks to the sun’s strong UV radiation. UV rays actually form free radicals that oxidize the tissues in your eyes. This is called solar retinopathy.

The dark spot is solar retinopathy, Credit: AAPOS/David L. Rogers, MD

It doesn’t take much time for this to happen — just a few seconds is enough. And you don’t know you’re damaging your retinas because it doesn’t hurt. The thing is, your eyes will keep working as the damage happens — so it’s not like all of a sudden, you’re looking at the sun and then you can’t see a thing, and that’s your signal that damage has started.

Nope, even when your photoreceptors are overloaded, they continue functioning. But when you’ve looked away from the sun, and given your eyes a chance to rest, you’ll notice things like blurry vision, an inability to focus, or a spot in the center of your vision. These symptoms might take up to 12 hours to manifest, and then disappear as your eyes have time to heal. They might be permanent.

Are your eyes more vulnerable during an eclipse?

You may have noticed we emphasize eye protection during an eclipse. But that’s not because the eclipse is more powerful than regular sunlight.

During the ordinary course of a day, you’re probably not going to be staring at the sun. It’s not exactly a comfortable thing to try and do. The only times I’ve looked at the sun (with proper eye protection of course) other than an eclipse is for looking at sunspots through solar binoculars. But during a partial eclipse, as the moon moves to cover the sun, some people think that because there’s less light, it’s safe to squint and try and look at the sun to see its crescent shape.

Credit: NASA/Aubrey Gemignani

This can also be an issue if you’re staring at the sun right after totality, when the moon fully blocks the sun in the sky. (Totality is the only time you can take off your glasses and look up during an eclipse, it’s not safe before or after totality.) The key issue here is that during a total eclipse, your surroundings get dark, and your eyes will dilate to let in more light. If you’re looking straight at the sun when it emerges from totality, and that scorching amount of light is let into your eyes when your eyes are dilated, it could damage your photoreceptors. That’s why it’s very important to be aware of how long totality will last wherever you are, and be cognizant of when to put your solar eclipse glasses back on.

And as a reminder: fake eclipse glasses have been an issue, and continue to be an issue, so don’t just order off eBay or Amazon. Selection is probably getting slim, but I recommend at this point ordering from a camera store like B&H Photo or Adorama, those glasses will be legit — and remember, if you want to photograph the eclipse, you will need a solar filter for your camera or phone. Same goes for if you want to observe the eclipse through a telescope or binoculars — grab some solar filters!!